The invention described here may be made, used and licensed by the or for the U.S. Government for governmental purposes without paying me any royalty.
In internal combustion engines, bolts are known that not only fasten engine components together but also allow lubricating or cooling fluid to flow between the components. A common type of such bolt is the so-called xe2x80x9cbanjoxe2x80x9d bolt, which has an internal passage along its length and a port at either end. Also common are bolts in holes oversized along the bolts"" shanks so that fluid can flow along the outside of the shanks. U.S. Pat. No. 4,881,926 to Aoki et al. shows features of both a banjo bolt and a bolt in an oversized hole. It is even known to provide bolts having grooves cut across the threads to create a fluid passageway (Japanese Patent Abstract 09021411 to Miura Kenji, Jan. 1, 1997).
Certain disadvantages exist in the known designs for bolts that permit fluid passage. Banjo bolts, for example, require internal axial drillings and cross drillings, and the axial drillings become more difficult as the bolt length increases. Bolts in oversized holes do not provide positive location and resistance to shear loads along the joint plane between two components connected by the bolt. Bolts with grooves along the threads must be aligned with complimentary grooves in bolt hole threads in order to be effective as flow passages.
I have invented a fastening arrangement wherein the bolt positively locates two components relative to one another, resists the aforementioned shear loads, allows fluid passage and is easier to fabricate than a banjo bolt. My bolt has two reduced-diameter shank sections that together comprise most of the bolt""s length. The reduced-diameter shank sections lower axial stiffness of the bolt, resulting in lower alternating stresses and greater fatigue life, which is especially desirable in aerospace applications. The reduced diameter sections define radial gaps with the bolt hole to allow fluid passage along the bolt. Between the reduced diameter sections is a full-diameter pilot, which is at the joint plane between the components, resists shear forces and accurately locates the components relative to each other. Axial or slightly helical grooves in the pilot allow fluid to flow across the pilot from one section of the reduced-diameter shank to another.